In the manufacture of continuous glass filaments, batch is loaded into a melter to create a glass composition. The batch is melted in a furnace and the glass flows through a refining process to one or more bushings in a filament forming apparatus. Typically, each bushing includes many nozzles or tips through which streams of molten glass flow. The quenched glass streams are mechanically pulled from the nozzles by a winding apparatus to form continuous glass filaments.
Regarding the melter portion of this process, a conventional melter is constructed as a large single tank. The environment within the melter is maintained to be relatively calm, especially during a controlled start-up. The melter takes a relatively long time to set-up and then bring to an operating temperature. For operation efficiency, the cycle of each type of glass composition is relatively long. Any undesired or unexpected stoppage in the process can be extremely expensive, as large amounts of glass material may be wasted. Further, an unexpected stoppage can also be dangerous since the process involves extreme heat, molten glass and combustible gases in a confined space.
Various new melter designs have been developed to overcome the negative qualities of a conventional melter. One type of new design is a submerged combustion melter. The heat sources for this type of melter are positioned within and at the bottom of the furnace, that is to say, in a submerged position below the pool of molten glass. In this submerged position, the environment within the melter is much more intense and violent than a conventional melter. The time to bring the melter to an operating temperature is much shorter than a conventional melter. For example, the melt and refine process time associated with a submerged combustion melter may be less than 4 hours.
One advantage of the submerged combustion melter is the ability of the operator to start and stop the melting process as needed. As such, the glass composition can be changed more readily, and the operator can respond to unexpected problems downstream in a much more prompt and inexpensive manner. Starting and stopping the melting process, however, requires a controlled start-up, including a preheating cycle, every time the melter is restarted.